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• Why does glGetString returns a NULL string

  - by snape

  I am trying my hands at GLFW library. I have written a basic program to get OpenGL renderer and vendor string. Here is the code #include <GL/glew.h> #include <GL/glfw.h> #include <cstdio> #include <cstdlib> #include <string> using namespace std; void shutDown(int returnCode) { printf("There was an error in running the code with error %d\n",returnCode); GLenum res = glGetError(); const GLubyte *errString = gluErrorString(res); printf("Error is %s\n", errString); glfwTerminate(); exit(returnCode); } int main() { // start GL context and O/S window using GLFW helper library if (glfwInit() != GL_TRUE) shutDown(1); if (glfwOpenWindow(0, 0, 0, 0, 0, 0, 0, 0, GLFW_WINDOW) != GL_TRUE) shutDown(2); // start GLEW extension handler glewInit(); // get version info const GLubyte* renderer = glGetString (GL_RENDERER); // get renderer string const GLubyte* version = glGetString (GL_VERSION); // version as a string printf("Renderer: %s\n", renderer); printf("OpenGL version supported %s\n", version); // close GL context and any other GLFW resources glfwTerminate(); return 0; } I googled this error and found out that we have to initialize the OpenGL context before calling glGetString(). Although I have initialized OpenGL context using glfwInit() but still the function returns a NULL string. Any ideas? Edit I have updated the code with error checking mechanisms. This code on running outputs the following There was an error in running the code with error 2 Error is no error

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• Determining explosion radius damage - Circle to Rectangle 2D

  - by Paul Renton

  One of the Cocos2D games I am working on has circular explosion effects. These explosion effects need to deal a percentage of their set maximum damage to all game characters (represented by rectangular bounding boxes as the objects in question are tanks) within the explosion radius. So this boils down to circle to rectangle collision and how far away the circle's radius is from the closest rectangle edge. I took a stab at figuring this out last night, but I believe there may be a better way. In particular, I don't know the best way to determine what percentage of damage to apply based on the distance calculated. Note : All tank objects have an anchor point of (0,0) so position is according to bottom left corner of bounding box. Explosion point is the center point of the circular explosion. TankObject * tank = (TankObject*) gameSprite; float distanceFromExplosionCenter; // IMPORTANT :: All GameCharacter have an assumed (0,0) anchor if (explosionPoint.x < tank.position.x) { // Explosion to WEST of tank if (explosionPoint.y <= tank.position.y) { //Explosion SOUTHWEST distanceFromExplosionCenter = ccpDistance(explosionPoint, tank.position); } else if (explosionPoint.y >= (tank.position.y + tank.contentSize.height)) { // Explosion NORTHWEST distanceFromExplosionCenter = ccpDistance(explosionPoint, ccp(tank.position.x, tank.position.y + tank.contentSize.height)); } else { // Exp center's y is between bottom and top corner of rect distanceFromExplosionCenter = tank.position.x - explosionPoint.x; } // end if } else if (explosionPoint.x > (tank.position.x + tank.contentSize.width)) { // Explosion to EAST of tank if (explosionPoint.y <= tank.position.y) { //Explosion SOUTHEAST distanceFromExplosionCenter = ccpDistance(explosionPoint, ccp(tank.position.x + tank.contentSize.width, tank.position.y)); } else if (explosionPoint.y >= (tank.position.y + tank.contentSize.height)) { // Explosion NORTHEAST distanceFromExplosionCenter = ccpDistance(explosionPoint, ccp(tank.position.x + tank.contentSize.width, tank.position.y + tank.contentSize.height)); } else { // Exp center's y is between bottom and top corner of rect distanceFromExplosionCenter = explosionPoint.x - (tank.position.x + tank.contentSize.width); } // end if } else { // Tank is either north or south and is inbetween left and right corner of rect if (explosionPoint.y < tank.position.y) { // Explosion is South distanceFromExplosionCenter = tank.position.y - explosionPoint.y; } else { // Explosion is North distanceFromExplosionCenter = explosionPoint.y - (tank.position.y + tank.contentSize.height); } // end if } // end outer if if (distanceFromExplosionCenter < explosionRadius) { /* Collision :: Smaller distance larger the damage */ int damageToApply; if (self.directHit) { damageToApply = self.explosionMaxDamage + self.directHitBonusDamage; [tank takeDamageAndAdjustHealthBar:damageToApply]; CCLOG(@"Explsoion-> DIRECT HIT with total damage %d", damageToApply); } else { // TODO adjust this... turning out negative for some reason... damageToApply = (1 - (distanceFromExplosionCenter/explosionRadius) * explosionMaxDamage); [tank takeDamageAndAdjustHealthBar:damageToApply]; CCLOG(@"Explosion-> Non direct hit collision with tank"); CCLOG(@"Damage to apply is %d", damageToApply); } // end if } else { CCLOG(@"Explosion-> Explosion distance is larger than explosion radius"); } // end if } // end if Questions: 1) Can this circle to rect collision algorithm be done better? Do I have too many checks? 2) How to calculate the percentage based damage? My current method generates negative numbers occasionally and I don't understand why (Maybe I need more sleep!). But, in my if statement, I ask if distance < explosion radius. When control goes through, distance/radius must be < 1 right? So 1 - that intermediate calculation should not be negative. Appreciate any help/advice!

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• A star algorithm implementation problems

  - by bryan226

  I’m having some trouble implementing the A* algorithm in a 2D tile based game. The problem is basically that the algorithm gets stuck when something gets in its direct way (e.g. walls) Note that it only allows Horizontal and Vertical movement. Here's a picture as it works fine across the map without something in its direct way: (Green tile = destination, Blue = In closed list, Green = in open list) This is what happens if I try to walk 'around' a wall: I calculate costs with the F = G + H formula: G = 1 Cost per Step H = 10 Cost per Step //Count how many tiles are between current-tile & destination-tile The functions: short c_astar::GuessH(short Startx,short Starty,short Destinationx,short Destinationy) { hgeVector Start, Destination; Start.x = Startx; Start.y = Starty; Destination.x = Destinationx; Destination.y = Destinationy; short a = 0; short b = 0; if(Start.x > Destination.x) a = Start.x - Destination.x; else a = Destination.x - Start.x; if(Start.y > Destination.y) b = Start.y - Destination.y; else b = Destination.y - Start.y; return (a+b)*10; } short c_astar::GuessG(short Startx,short Starty,short Currentx,short Currenty) { hgeVector Start, Destination; Start.x = Startx; Start.y = Starty; Destination.x = Currentx; Destination.y = Currenty; short a = 0; short b = 0; if(Start.x > Destination.x) a = Start.x - Destination.x; else a = Destination.x - Start.x; if(Start.y > Destination.y) b = Start.y - Destination.y; else b = Destination.y - Start.y; return (a+b); } At the end of the loop I check which tile is the cheapest to go according to its F value: Then some quick checks are done for each tile (UP,DOWN,LEFT,RIGHT): //...CX are holding the F value of the TILE specified // Info: C0 = Center (Current) // C1 = UP // C2 = DOWN // C3 = LEFT // C4 = RIGHT //Quick checks if(((C1 < C2) && (C1 < C3) && (C1 < C4))) { Current.y -= 1; bSimilar = false; if(DEBUG) hge->System_Log("C1 < ALL"); } //.. same for C2,C3 & C4 If there are multiple tiles with the same F value: It’s actually a switch for DOWNLEFT,UPRIGHT.. etc. Here’s one of it: case UPRIGHT: { //UP Temporary = Current; Temporary.y -= 1; bTileStatus[0] = IsTileWalkable(Temporary.x,Temporary.y); if(bTileStatus[0]) { //Proceed normal we are OK & walkable Tilex.Tile = map.at(Temporary.y).at(Temporary.x); //Search in lists if(SearchInClosedList(Tilex.Tile.ID,C0)) bFoundInClosedList[0] = true; if(SearchInOpenList(Tilex.Tile.ID,C0)) bFoundInOpenList[0] = true; //RIGHT Temporary = Current; Temporary.x += 1; bTileStatus[1] = IsTileWalkable(Temporary.x,Temporary.y); if(bTileStatus[1]) { //Proceed normal we are OK & walkable Tilex.Tile = map.at(Temporary.y).at(Temporary.x); //Search in lists if(SearchInClosedList(Tilex.Tile.ID,C0)) bFoundInClosedList[1] = true; if(SearchInOpenList(Tilex.Tile.ID,C0)) bFoundInOpenList[1] = true; //************************************************* // Purpose: ClosedList behavior //************************************************* if(bFoundInClosedList[0] && !bFoundInClosedList[1]) { //UP found in ClosedList. Go RIGHT return RIGHT; } if(!bFoundInClosedList[0] && bFoundInClosedList[1]) { //RIGHT found in ClosedList. Go UP return UP; } if(bFoundInClosedList[0] && bFoundInClosedList[1]) { //Both found in ClosedList. Random value switch(hge->Random_Int(8,9)) { case 8: return UP; break; case 9: return RIGHT; break; } } //************************************************* // Purpose: OpenList behavior //************************************************* if(bFoundInOpenList[0] && !bFoundInOpenList[1]) { //UP found in OpenList. Go RIGHT return RIGHT; } if(!bFoundInOpenList[0] && bFoundInOpenList[1]) { //RIGHT found in OpenList. Go UP return UP; } if(bFoundInOpenList[0] && bFoundInOpenList[1]) { //Both found in OpenList. Random value switch(hge->Random_Int(8,9)) { case 8: return UP; break; case 9: return RIGHT; break; } } } else if(!bTileStatus[1]) { //RIGHT is not walkable OR out of range //Choose UP return UP; } } else if(!bTileStatus[0]) { //UP is not walkable OR out of range //Fast check RIGHT Temporary = Current; Temporary.x += 1; bTileStatus[1] = IsTileWalkable(Temporary.x,Temporary.y); if(bTileStatus[1]) { return RIGHT; } else return FAILED; //Failed, no valid path found! } } break; A log for the second picture: (Cut down to ten passes, because it’s just repeating itself) ----------------------------------------------------- PASS: 1 | C1: 211 | C2: 191 | C3: 211 | C4: 191 DOWN + RIGHT SIMILAR Going DOWN ----------------------------------------------------- PASS: 2 | C1: 200 | C2: 182 | C3: 202 | C4: 182 DOWN + RIGHT SIMILAR Going DOWN ----------------------------------------------------- PASS: 3 | C1: 191 | C2: 193 | C3: 193 | C4: 173 C4 < ALL Tile(12.000000,6.000000) not walkable. MAX_F_VALUE set. ----------------------------------------------------- PASS: 4 | C1: 182 | C2: 184 | C3: 182 | C4: 999 UP + LEFT SIMILAR Going UP Tile(12.000000,5.000000) not walkable. MAX_F_VALUE set. ----------------------------------------------------- PASS: 5 | C1: 191 | C2: 173 | C3: 191 | C4: 999 C2 < ALL Tile(12.000000,6.000000) not walkable. MAX_F_VALUE set. ----------------------------------------------------- PASS: 6 | C1: 182 | C2: 184 | C3: 182 | C4: 999 UP + LEFT SIMILAR Going UP Tile(12.000000,5.000000) not walkable. MAX_F_VALUE set. ----------------------------------------------------- PASS: 7 | C1: 191 | C2: 173 | C3: 191 | C4: 999 C2 < ALL Tile(12.000000,6.000000) not walkable. MAX_F_VALUE set. ----------------------------------------------------- PASS: 8 | C1: 182 | C2: 184 | C3: 182 | C4: 999 UP + LEFT SIMILAR Going LEFT ----------------------------------------------------- PASS: 9 | C1: 191 | C2: 193 | C3: 193 | C4: 173 C4 < ALL Tile(12.000000,6.000000) not walkable. MAX_F_VALUE set. ----------------------------------------------------- PASS: 10 | C1: 182 | C2: 184 | C3: 182 | C4: 999 UP + LEFT SIMILAR Going LEFT ----------------------------------------------------- Its always going after the cheapest F value, which seems to be wrong. If someone could point me to the right direction I'd be thankful. Regards, bryan226

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• Ruby: implementing alpha-beta pruning for tic-tac-toe

  - by DerNalia

  So, alpha-beta pruning seems to be the most efficient algorithm out there aside from hard coding (for tic tac toe). However, I'm having problems converting the algorithm from the C++ example given in the link: http://www.webkinesia.com/games/gametree.php #based off http://www.webkinesia.com/games/gametree.php # (converted from C++ code from the alpha - beta pruning section) # returns 0 if draw LOSS = -1 DRAW = 0 WIN = 1 @next_move = 0 def calculate_ai_next_move score = self.get_best_move(COMPUTER, WIN, LOSS) return @next_move end def get_best_move(player, alpha, beta) best_score = nil score = nil if not self.has_available_moves? return false elsif self.has_this_player_won?(player) return WIN elsif self.has_this_player_won?(1 - player) return LOSS else best_score = alpha NUM_SQUARES.times do |square| if best_score >= beta break end if self.state[square].nil? self.make_move_with_index(square, player) # set to negative of opponent's best move; we only need the returned score; # the returned move is irrelevant. score = -get_best_move(1-player, -beta, -alpha) if (score > bestScore) @next_move = square best_score = score end undo_move(square) end end end return best_score end the problem is that this is returning nil. some support methods that are used above: WAYS_TO_WIN = [[0, 1, 2], [3, 4, 5], [6, 7, 8], [0, 3, 6], [1, 4, 7], [2, 5, 8],[0, 4, 8], [2, 4, 6]] def has_this_player_won?(player) result = false WAYS_TO_WIN.each {|solution| result = self.state[solution[0]] if contains_win?(solution) } return (result == player) end def contains_win?(ttt_win_state) ttt_win_state.each do |pos| return false if self.state[pos] != self.state[ttt_win_state[0]] or self.state[pos].nil? end return true end def make_move(x, y, player) self.set_square(x,y, player) end

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• GoogleAppEngine : ClassNotFoundException : javax.jdo.metadata.ComponentMetadata

  - by James.Elsey

  I'm trying to deploy my application to a locally running GoogleAppEngine development server, but I'm getting the following stack trace when I start the server Apr 23, 2010 9:03:33 PM com.google.apphosting.utils.jetty.JettyLogger warn WARNING: Nested in org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'clientDao' defined in ServletContext resource [/WEB-INF/applicationContext.xml]: Cannot resolve reference to bean 'entityManagerFactory' while setting bean property 'entityManagerFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in ServletContext resource [/WEB-INF/applicationContext.xml]: Invocation of init method failed; nested exception is java.lang.NoClassDefFoundError: javax/jdo/metadata/ComponentMetadata: java.lang.ClassNotFoundException: javax.jdo.metadata.ComponentMetadata at java.net.URLClassLoader$1.run(URLClassLoader.java:217) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:205) at java.lang.ClassLoader.loadClass(ClassLoader.java:319) at com.google.appengine.tools.development.IsolatedAppClassLoader.loadClass(IsolatedAppClassLoader.java:151) at java.lang.ClassLoader.loadClass(ClassLoader.java:264) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:332) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:264) at javax.jdo.JDOHelper$18.run(JDOHelper.java:2009) at javax.jdo.JDOHelper$18.run(JDOHelper.java:2007) at java.security.AccessController.doPrivileged(Native Method) at javax.jdo.JDOHelper.forName(JDOHelper.java:2006) at javax.jdo.JDOHelper.invokeGetPersistenceManagerFactoryOnImplementation(JDOHelper.java:1155) at javax.jdo.JDOHelper.getPersistenceManagerFactory(JDOHelper.java:803) at javax.jdo.JDOHelper.getPersistenceManagerFactory(JDOHelper.java:698) at org.datanucleus.jpa.EntityManagerFactoryImpl.initialisePMF(EntityManagerFactoryImpl.java:482) at org.datanucleus.jpa.EntityManagerFactoryImpl.<init>(EntityManagerFactoryImpl.java:255) at org.datanucleus.store.appengine.jpa.DatastoreEntityManagerFactory.<init>(DatastoreEntityManagerFactory.java:68) at org.datanucleus.store.appengine.jpa.DatastorePersistenceProvider.createContainerEntityManagerFactory(DatastorePersistenceProvider.java:45) at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:224) at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:291) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1369) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1335) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:473) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409) at java.security.AccessController.doPrivileged(Native Method) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164) at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:269) at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:104) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1245) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1010) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:472) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409) at java.security.AccessController.doPrivileged(Native Method) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:429) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:728) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:380) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:255) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:45) at org.mortbay.jetty.handler.ContextHandler.startContext(ContextHandler.java:530) at org.mortbay.jetty.servlet.Context.startContext(Context.java:135) at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1218) at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:500) at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:448) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:40) at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:117) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:40) at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:117) at org.mortbay.jetty.Server.doStart(Server.java:217) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:40) at com.google.appengine.tools.development.JettyContainerService.startContainer(JettyContainerService.java:181) at com.google.appengine.tools.development.AbstractContainerService.startup(AbstractContainerService.java:116) at com.google.appengine.tools.development.DevAppServerImpl.start(DevAppServerImpl.java:217) at com.google.appengine.tools.development.DevAppServerMain$StartAction.apply(DevAppServerMain.java:162) at com.google.appengine.tools.util.Parser$ParseResult.applyArgs(Parser.java:48) at com.google.appengine.tools.development.DevAppServerMain.<init>(DevAppServerMain.java:113) at com.google.appengine.tools.development.DevAppServerMain.main(DevAppServerMain.java:89) The server is running at http://localhost:1234/ I'm a little confused over this, since I have the same application running locally on GlassFish/MySQL. All I have done is to swap in the relevant jar files, and change the persistence.xml. My applicationContext.xml looks as follows : <context:annotation-config/> <bean id="clientDao" class="com.jameselsey.salestracker.dao.jpa.JpaDaoClient"> <property name="entityManagerFactory" ref="entityManagerFactory"/> </bean> <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"/> <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager"> <property name="entityManagerFactory" ref="entityManagerFactory" /> </bean> <bean id="org.springframework.context.annotation.internalPersistenceAnnotationProcessor" class="com.jameselsey.salestracker.util.GaeFixInternalPersistenceAnnotationProcessor" /> <bean class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor"/> <tx:annotation-driven/> <bean id="clientService" class="com.jameselsey.salestracker.service.ClientService"/> </beans> My JPA DAO looks like this public class JpaDao extends JpaDaoSupport { protected <T> List<T> findAll(Class<T> clazz) { return getJpaTemplate().find("select c from " + clazz.getName() + " c"); } protected <T> T findOne(String jpql, Map params) { List<T> results = getJpaTemplate().findByNamedParams(jpql, params); if(results.isEmpty()) { return null; } if(results.size() > 1) { throw new IncorrectResultSizeDataAccessException(1, results.size()); } return results.get(0); } } And an example implemented method looks like this : @Override public Client getClientById(Integer clientId) { String jpql = "SELECT c " + "FROM com.jameselsey.salestracker.domain.Client c " + "WHERE c.id = " + clientId; return (Client) getJpaTemplate().find(jpql).get(0); } Like I say, this works ok on Glassfish/MySQL, is it possible this error could be a red herring to something else?

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• OpenGL Shading Program Object Memory Requirement

  - by Hans Wurst

  gDEbugger states that OpenGL's program objects only occupy an insignificant amount of memory. How much is this actually? I don't know if the stuff I looked up in mesa is actually that I was looking for but it requires 16KB [Edit: false, confusing struct names, less than 1KB immediate, some further behind pointers] per program object. Not quite insignificant. So is it recommended to create a unique program object for each object of the scene? Or to share a single program object and set the scene's object's custom variables just before its draw call?

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• HLSL - Creating Shadows in 2D

  - by richard

  The way that I create shadows is by the following technique: http://www.catalinzima.com/2010/07/my-technique-for-the-shader-based-dynamic-2d-shadows/ But I have questions to HLSL. The way that I currently do it is, I have a black and white image, where Black means 'object', and white means 'nothing'. I then distort the image like in the tutorial. I do this with a pixel shader, but instead of rendering to the screen, I render to a texture, back to my application. I then take this, and create the shadows, and then send it back to the graphics card to undo the distortion, after the shadow has been added - this comes back and I have a stencil of shadow. I can put this ontop of the original image and send them back to the graphics card, which then puts them on the screen. To me this is alot of back and forth. Is there a way i can avoid this? The problem that I am having is that I need to basically go through all positions in the texture 3 times, and use the new new texture every time instead of the orginal one. I tried to read up on Passes, but i don't think that i am heading in the right direction there. Help?

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• Draw multiple objects with textures

  - by Simplex

  I want to draw cubes using textures. void OperateWithMainMatrix(ESContext* esContext, GLfloat offsetX, GLfloat offsetY, GLfloat offsetZ) { UserData *userData = (UserData*) esContext->userData; ESMatrix modelview; ESMatrix perspective; //Manipulation with matrix ... glVertexAttribPointer(userData->positionLoc, 3, GL_FLOAT, GL_FALSE, 0, cubeFaces); //in cubeFaces coordinates verticles cube glVertexAttribPointer(userData->normalLoc, 3, GL_FLOAT, GL_FALSE, 0, cubeFaces); //for normals (use in fragment shaider for textures) glEnableVertexAttribArray(userData->positionLoc); glEnableVertexAttribArray(userData->normalLoc); // Load the MVP matrix glUniformMatrix4fv(userData->mvpLoc, 1, GL_FALSE, (GLfloat*)&userData->mvpMatrix.m[0][0]); //Bind base map glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_CUBE_MAP, userData->baseMapTexId); //Set the base map sampler to texture unit to 0 glUniform1i(userData->baseMapLoc, 0); // Draw the cube glDrawArrays(GL_TRIANGLES, 0, 36); } (coordinates transformation is in OperateWithMainMatrix() ) Then Draw() function is called: void Draw(ESContext *esContext) { UserData *userData = esContext->userData; // Set the viewport glViewport(0, 0, esContext->width, esContext->height); // Clear the color buffer glClear(GL_COLOR_BUFFER_BIT); // Use the program object glUseProgram(userData->programObject); OperateWithMainMatrix(esContext, 0.0f, 0.0f, 0.0f); eglSwapBuffers(esContext->eglDisplay, esContext->eglSurface); } This work fine, but if I try to draw multiple cubes (next code for example): void Draw(ESContext *esContext) { ... // Use the program object glUseProgram(userData->programObject); OperateWithMainMatrix(esContext, 2.0f, 0.0f, 0.0f); OperateWithMainMatrix(esContext, 1.0f, 0.0f, 0.0f); OperateWithMainMatrix(esContext, 0.0f, 0.0f, 0.0f); OperateWithMainMatrix(esContext, -1.0f, 0.0f, 0.0f); OperateWithMainMatrix(esContext, -2.0f, 0.0f, 0.0f); eglSwapBuffers(esContext->eglDisplay, esContext->eglSurface); } A side faces overlapes frontal face. The side face of the right cube overlaps frontal face of the center cube. How can i remove this effect and display miltiple cubes without it?

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• Animating DOM elements vs refreshing a single Canvas

  - by mgibsonbr

  A few years ago, when the HTML Canvas element was still kinda fresh, I wrote a small game in a rather "unusual" way: each game element had its own canvas, and frequently animated elements even had multiple canvases, one for each animation sprite. This way, the translation would be done by manipulating the DOM position of the canvases, while the sprite animation would consist of altering the visibility of the already drawn canvases. (z-indexes, of course, were the tricky part) It worked like a charm: even in IE6 with excanvas it showed a decent performance, and everything was rather consistent between browsers, including some smartphones. Now I'm thinking in writing a larger game engine in the same fashion, so I'm wondering whether it would be a good idea to do so in the current context (with all the advances in browsers and so on). I know I'm trading memory for time, so this needs to be customizable (even at runtime) for each machine the game will be running. But I believe using separate canvases would also help to avoid the game "freezing" on CPU spikes, since the translation would still happen even if the redraws lag for a while. Besides, the browsers' rendering engines are already optimized in may ways, so I'm guessing this scheme would also reduce the load on the CPU (in contrast to doing everything in JavaScript - specially the less optimized ones). It looks good in my head, but I'd like to hear the opinion of more experienced people before proceeding further. Is there any known drawback of doing this? I'm particulartly unexperienced in dealing with the GPU, so I wonder whether this "trick" would nullify any benefit of using a single, big canvas. Or maybe on modern devices it's overkill (though I'm skeptic about the claims that canvas+js - especially WebGL - will ever be a good alternative to native code). Any thoughts?

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• Double sides face with two normals

  - by Marnix

  I think this isn't possible, but I just want to check this: Is it possible to create a face in opengl that has two normals? So: I want the inside and outside of some cilinder to be drawn, but I want the lights to do as expected and not calculate it for the normal given. I was trying to do this with backface culling off, so I would have both faces, but the light was wrongly calculated of course. Is this possible, or do I have to draw an inside and an outside? So draw twice?

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• Painting with pixel shaders

  - by Gustavo Maciel

  I have an almost full understanding of how 2D Lighting works, saw this post and was tempted to try implementing this in HLSL. I planned to paint each of the layers with shaders, and then, combine them just drawing one on top of another, or just pass the 3 textures to the shader and getting a better way to combine them. Working almost as planned, but I got a little question in the matter. I'm drawing each layer this way: GraphicsDevice.SetRenderTarget(lighting); GraphicsDevice.Clear(Color.Transparent); //... Setup shader SpriteBatch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend, SamplerState.LinearClamp, DepthStencilState.None, RasterizerState.CullNone, lightingShader); SpriteBatch.Draw(texture, fullscreen, Color.White); SpriteBatch.End(); GraphicsDevice.SetRenderTarget(darkMask); GraphicsDevice.Clear(Color.Transparent); //... Setup shader SpriteBatch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend, SamplerState.LinearClamp, DepthStencilState.None, RasterizerState.CullNone, darkMaskShader); SpriteBatch.Draw(texture, fullscreen, Color.White); SpriteBatch.End(); Where lightingShader and darkMaskShader are shaders that, with parameters (view and proj matrices, light pos, color and range, etc) generate a texture meant to be that layer. It works fine, but I'm not sure if drawing a transparent quad on top of a transparent render target is the best way of doing it. Because I actually just need the position and params. Concluding: Can I paint a texture with shaders without having to clear it and then draw a transparent texture on top of it?

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• Open GL Android frame-by-frame animation tutorial/example code

  - by Trick

  My first question was asked wrong, so I need to ask again :) I found out, that I will have to do an OpenGL animation for my Android game. The closest (known) example is Talking Tom (but I don't know how they did the animations). I have large PNGs which I would like to put into a animation. For example - 30 PNGs 427×240px at 8 FPS. I know some things already about Open GL, but I am used to learn from example code. And it is quicker that way (so I don't need to invent hot water all over again :)). Does anybody has any points to direct me?

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• 2D XNA C#: Texture2D Wrapping Issue

  - by Kieran

  Working in C#/XNA for a Windows game: I'm using Texture2D to draw sprites. All of my sprites are 16 x 32. The sprites move around the screen as you would expect, by changing the top X/Y position of them when they're being drawn by the spritebatch. Most of the time when I run the game, the sprites appear like this: and when moved, they move as I expect, as one element. Infrequently they appear like this: and when moved it's like there are two sprites with a gap in between them - it's hard to describe. It only seems to happen sometimes - is there something I'm missing? I'd really like to know why this is happening. [Edit:] Adding Draw code as requested: This is the main draw routine - it first draws the sprite to a RenderTarget then blows it up by a scale of 4: protected override void Draw(GameTime gameTime) { // Draw to render target GraphicsDevice.SetRenderTarget(renderTarget); GraphicsDevice.Clear(Color.CornflowerBlue); Texture2D imSprite = null; spriteBatch.Begin(SpriteSortMode.FrontToBack, null, SamplerState.PointWrap, null, null); ManSprite.Draw(spriteBatch); base.Draw(gameTime); spriteBatch.End(); // Draw render target to screen GraphicsDevice.SetRenderTarget(null); imageFrame = (Texture2D)renderTarget; GraphicsDevice.Clear(ClearOptions.Target | ClearOptions.DepthBuffer, Color.DarkSlateBlue, 1.0f, 0); spriteBatch.Begin(SpriteSortMode.FrontToBack, null, SamplerState.PointClamp, null, null); spriteBatch.Draw(imageFrame, new Vector2(0, 0), null, Color.White, 0, new Vector2(0, 0), IM_SCALE, SpriteEffects.None, 0); spriteBatch.End(); } This is the draw routine for the Sprite class: public virtual void Draw(SpriteBatch spriteBatch) { spriteBatch.Draw(Texture, new Vector2(PositionX, PositionY), null, Color.White, 0.0f, Vector2.Zero, Scale, SpriteEffects.None, 0.3f); }

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• Example of DOD design (on a generic Zombie game)

  - by Jeffrey

  I can't seem to find a nice explanation of the Data Oriented Design for a generic zombie game (it's just an example, pretty common example). Could you make an example of the Data Oriented Design on creating a generic zombie class? Is the following good? Zombie list class: class ZombieList { GLuint vbo; // generic zombie vertex model std::vector<color>; // object default color std::vector<texture>; // objects textures std::vector<vector3D>; // objects positions public: unsigned int create(); // return object id void move(unsigned int objId, vector3D offset); void rotate(unsigned int objId, float angle); void setColor(unsigned int objId, color c); void setPosition(unsigned int objId, color c); void setTexture(unsigned int, unsigned int); ... void update(Player*); // move towards player, attack if near } Example: Player p; Zombielist zl; unsigned int first = zl.create(); zl.setPosition(first, vector3D(50, 50)); zl.setTexture(first, texture("zombie1.png")); ... while (running) { // main loop ... zl.update(&p); zl.draw(); // draw every zombie } Or would creating a generic World container that contains every action from bite(zombieId, playerId) to moveTo(playerId, vector) to createPlayer() to shoot(playerId, vector) to face(radians)/face(vector); and contains: std::vector<zombie> std::vector<player> ... std::vector<mapchunk> ... std::vector<vbobufferid> player_run_animation; ... be a good example? Whats the proper way to organize a game with DOD?

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• Generating geometry when using VBO

  - by onedayitwillmake

  Currently I am working on a project in which I generate geometry based on the players movement. A glorified very long trail, composed of quads. I am doing this by storing a STD::Vector, and removing the oldest verticies once enough exist, and then calling glDrawArrays. I am interested in switching to a shader based model, usually examples I see the VBO is generated at start and then that's basically it. What is the best route to go about creating geometry in real time, using shader / VBO approach

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• matrix 4x4 position data

  - by freefallr

  I understand that a 4x4 matrix holds rotation and position data. The rotation data is held in the 3x3 sub-matrix at the top left of the matrix. The position data is held in the last column of the matrix. e.g. glm::vec3 vParentPos( mParent[3][0], mParent[3][1], mParent[3][2] ); My question is - am I accessing the parent matrix correctly in the example above? I know that opengl uses a different matrix ordering that directx, (row order instead of column order or something), so, should the mParent be accessed as follows instead? glm::vec3 vParentPos( mParent[0][3], mParent[1][3], mParent[2][3] ); thanks!

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• Bitmap font rendering, UV generation and vertex placement

  - by jack

  I am generating a bitmap, however, I am not sure on how to render the UV's and placement. I had a thread like this once before, but it was too loosely worded as to what I was looking to do. What I am doing right now is creating a large 1024x1024 image with characters evenly placed every 64 pixels. Here is an example of what I mean. I then save the bitmap X/Y information to a file (which is all multiples of 64). However, I am not sure how to properly use this information and bitmap to render. This falls into two different categories, UV generation and kerning. Now I believe I know how to do both of these, however, when I attempt to couple them together I will get horrendous results. For example, I am trying to render two different text arrays, "123" and "njfb". While ignoring the texture quality (I will be increasing the texture to provide more detail once I fix this issue), here is what it looks like when I try to render them. http://img64.imageshack.us/img64/599/badfontrendering.png Now for the algorithm. I am doing my letter placement with both GetABCWidth and GetKerningPairs. I am using GetABCWidth for the width of the characters, then I am getting the kerning information for adjust the characters. Does anyone have any suggestions on how I can implement my own bitmap font renderer? I am trying to do this without using external libraries such as angel bitmap tool or freetype. I also want to stick to the way the bitmap font sheet is generated so I can do extra effects in the future. Rendering Algorithm for(U32 c = 0, vertexID = 0, i = 0; c < numberOfCharacters; ++c, vertexID += 4, i += 6) { ObtainCharInformation(fontName, m_Text[c]); letterWidth = (charInfo.A + charInfo.B + charInfo.C) * scale; if(c != 0) { DWORD BytesReq = GetGlyphOutlineW(dc, m_Text[c], GGO_GRAY8_BITMAP, &gm, 0, 0, &mat); U8 * glyphImg= new U8[BytesReq]; DWORD r = GetGlyphOutlineW(dc, m_Text[c], GGO_GRAY8_BITMAP, &gm, BytesReq, glyphImg, &mat); for (int k=0; k<nKerningPairs; k++) { if ((kerningpairs[k].wFirst == previousCharIndex) && (kerningpairs[k].wSecond == m_Text[c])) { letterBottomLeftX += (kerningpairs[k].iKernAmount * scale); break; } } letterBottomLeftX -= (gm.gmCellIncX * scale); } SetVertex(letterBottomLeftX, 0.0f, zFight, vertexID); SetVertex(letterBottomLeftX, letterHeight, zFight, vertexID + 1); SetVertex(letterBottomLeftX + letterWidth, letterHeight, zFight, vertexID + 2); SetVertex(letterBottomLeftX + letterWidth, 0.0f, zFight, vertexID + 3); zFight -= 0.001f; float BottomLeftX = (F32)(charInfo.bitmapXOrigin) / (float)m_BitmapWidth; float BottomLeftY = (F32)(charInfo.bitmapYOrigin + charInfo.charBitmapHeight) / (float)m_BitmapWidth; float TopLeftX = BottomLeftX; float TopLeftY = (F32)(charInfo.bitmapYOrigin) / (float)m_BitmapWidth; float TopRightX = (F32)(charInfo.bitmapXOrigin + charInfo.B - charInfo.C) / (float)m_BitmapWidth; float TopRightY = TopLeftY; float BottomRightX = TopRightX; float BottomRightY = BottomLeftY; SetTextureCoordinate(TopLeftX, TopLeftY, vertexID + 1); SetTextureCoordinate(BottomLeftX, BottomLeftY, vertexID + 0); SetTextureCoordinate(BottomRightX, BottomRightY, vertexID + 3); SetTextureCoordinate(TopRightX, TopRightY, vertexID + 2); /// index setting letterBottomLeftX += letterWidth; previousCharIndex = m_Text[c]; }

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• How to handle a player's level and its consequent privileges?

  - by Songo

  I'm building a game similar to Mafia Wars where a player can do tasks for his gang and gain experience and thus advancing his level. The game is built using PHP and a Mysql database. In the game I want to limit the resources allowed to player based on his level. For example: ________| (Max gold) | (Max army size) | (Max moves) | ... Level 1 | 1000 | 100 | 10 | ... Level 2 | 1500 | 200 | 20 | ... Level 3 | 3000 | 300 | 25 | ... . . . In addition certain features of the game won't be allowed until a certain level is reached such as players under Level 10 can't trade in the game market, players under Level 20 can't create alliances,...etc. The way I have modeled it is by implementing a very loooong ACL (Access Control List) with about 100 entries (an entry for each level). However, I think there may be a simpler approach to this seeing that this feature have been implemented in many games before.

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• How to move Objects smoothly like swimming arround

  - by philipp

  I have a Box2D project that is about to create a view where the user looks from the Sky onto Water. Or perhaps on a bathtub filled with water or something like this. The Object which holds the fluid actually does not matter, what matters is the movement of the bodies, because they should move like drops of grease on a soup, or wood on water, I can even imagine the the fluid is mercurial, extreme heavy and "lazy". How can I manipulate the bodies (every frame or time by time) to make them move like this? I started with randomly manipulation their linear velocity, but I turned out that this not very smooth and looks quite hard. Is it a better idea to check their velocity and apply impulses? Is there any example? Greetings philipp

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• Sounds to describe the weather?

  - by Matthew

  I'm trying to think of sounds that will help convey the time of day and weather condition. I'm not even sure of all the weather conditions I would consider, and some are obvious. Like if it's raining, the sound of rain. But then I'm thinking, what about for a calm day? If it's morning time, I could do birds chirping or something. Night time could be an owl or something. What are some good combinations of sounds/weather/time to have a good effect?

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• Unity-Animation parameters are not being set

  - by user1814893

  I have the following animation controller: with two parameters of walkingSpeed and Jump. I have the following code which should change the values: animator.SetFloat("walkingSpeed",0.9f); animator.SetBool("Jump",true); and animator is the correctly referenced animator object. However the values that the parameters are set to do not appear to change in the animator window, nor do they appear to impact what is happening on the screen. However they do seem to impact the values obtained when doing the following: animator.GetFloat("walkingSpeed"); The animator consists of the shown blend tree, which works correctly and is always active, however due to the values not being changed it does not blends, and always acts as if the value with which it blends (walkingSpeed is 0). What is going on?

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• OpenGL Tessellation makes point

  - by urza57

  A little problem with my tessellation shader. I try to implement a simple tessellation shader but it only makes points. Here's my vertex shader : out vec4 ecPosition; out vec3 ecNormal; void main( void ) { vec4 position = gl_Vertex; gl_Position = gl_ModelViewProjectionMatrix * position; ecPosition = gl_ModelViewMatrix * position; ecNormal = normalize(gl_NormalMatrix * gl_Normal); } My tessellation control shader : layout(vertices = 3) out; out vec4 ecPosition3[]; in vec3 ecNormal[]; in vec4 ecPosition[]; out vec3 myNormal[]; void main() { gl_out[gl_InvocationID].gl_Position = gl_in[gl_InvocationID].gl_Position; myNormal[gl_InvocationID] = ecNormal[gl_InvocationID]; ecPosition3[gl_InvocationID] = ecPosition[gl_InvocationID]; gl_TessLevelOuter[0] = float(4.0); gl_TessLevelOuter[1] = float(4.0); gl_TessLevelOuter[2] = float(4.0); gl_TessLevelInner[0] = float(4.0); } And my Tessellation Evaluation shader: layout(triangles, equal_spacing, ccw) in; in vec3 myNormal[]; in vec4 ecPosition3[]; out vec3 ecNormal; out vec4 ecPosition; void main() { float u = gl_TessCoord.x; float v = gl_TessCoord.y; float w = gl_TessCoord.z; vec3 position = vec4(gl_in[0].gl_Position.xyz * u + gl_in[1].gl_Position.xyz * v + gl_in[2].gl_Position.xyz * w ); vec3 position2 = vec4(ecPosition3[0].xyz * u + ecPosition3[1].xyz * v + ecPosition3[2].xyz * w ); vec3 normal = myNormal[0] * u + myNormal[1] * v + myNormal[2] * w ); ecNormal = normal; gl_Position = vec4(position, 1.0); ecPosition = vec4(position2, 1.0); } Thank you !

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• Need help about Drag a sprite with Animation (Cocos2d)

  - by Zishan

  I want to play an animation when someone drag a sprite from it's default position to another selected position. If he drag half of the selected position then animation will be play half. Example, I have 15 Frames of a animation and have a projectile arm. The projectile arm can be rotate maximum 30°, if someone rotate the arm 2° then animation sprite will be show 2nd frame, if rotate 12° then animation sprite will be show 6th frame.... and so on. Also when he release the arm, then the arm will be reverse back to it's default position and animation frames also will be reverse back to it's default first frame. I am new on cocos2d.I know how to make an animation and how to drag a sprite but I have no idea how to do this. Can anyone Please give me any idea or any tutorial how to do this, it will be very helpful for me. Thank you in advance.

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• Rotating an object about a point (2D) using box2d

  - by noob

  i just started developing using box2d on flixel and i realise the pivot point of the rotation of an object in box2d is set to the center of an object. i had read on forums and i found out that SetAsBox can change the pivot point of the object, however, i cannot seem to get it work to rotate about a point. what i would like to achieve is to rotate an object about a point like earth revolving around the sun. any one can help me with it? really thanks a lot and sorry for the bad english

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• Doing powerups in a component-based system

  - by deft_code

  I'm just starting really getting my head around component based design. I don't know what the "right" way to do this is. Here's the scenario. The player can equip a shield. The the shield is drawn as bubble around the player, it has a separate collision shape, and reduces the damage the player receives from area effects. How is such a shield architected in a component based game? Where I get confused is that the shield obviously has three components associated with it. Damage reduction / filtering A sprite A collider. To make it worse different shield variations could have even more behaviors, all of which could be components: boost player maximum health health regen projectile deflection etc Am I overthinking this? Should the shield just be a super component? I really think this is wrong answer. So if you think this is the way to go please explain. Should the shield be its own entity that tracks the location of the player? That might make it hard to implement the damage filtering. It also kinda blurs the lines between attached components and entities. Should the shield be a component that houses other components? I've never seen or heard of anything like this, but maybe it's common and I'm just not deep enough yet. Should the shield just be a set of components that get added to the player? Possibly with an extra component to manage the others, e.g. so they can all be removed as a group. (accidentally leave behind the damage reduction component, now that would be fun). Something else that's obvious to someone with more component experience?

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